Respiration equipment may be divided into two main classes. The first class, namely resuscitators, are generally speaking designed for reviving a patient who has either ceased breathing, or who is breathling only with great difficulty. The other type of equipment, namely inhalators, supply gases or gas mixtures such as anaesthetics, or oxygen enriched air for speeding up the revival of a person who either has previously been revived with a resuscitator, or who is experiencing some respiration difficulty, and requires assistance.
In the great majority of cases, it is highly desirable to have the two functions namely the resuscitator function and the inhalator function provided by the same piece of respiration equipment, with complete and instantaneous control over both functions without the need for leaving the patient to attend to a complex system of valves and gauges. In the past, dual-purpose apparatus of this kind has been available but has been of such a complex and cumbersome nature that either the operator would have to turn away from the patient to attend to various dials and gauges, or he would require an assistant. The desired coordination of the assistant handling the controls, with the operator who is actually in charge of the patient was of course quite difficult to achieve in many circumstances.
In addition, it is desirable to provide such a piece of equipment which can be operated in a simple foolproof manner by relatively unskilled personnel. It is of course be borne in mind that in many cases equipment of this kind is used in an emergency by the first person who is available to assist a casualty. Such a person will only in very rare cases be a highly trained medical assistant. In the great majority of cases such a person may be for example a lifeguard or swimming pool attendant, or a person on duty at an electrical generating station for example, or may be a relatively untrained fireman. In addition, the environment where such treatment is given is rarely if ever conducive to the careful and methodical application of professional medical skills. On the contrary, such an environment may be for example, several hundred feet under ground in a mine shaft, or at a breakdown in a generating or transformer station, or at the location of a fire. Such equipment must therefore be adapted for use by such relatively untrained personnel, who may in addition, be under considerable emotional or nervous strain due to the circumstances and the surroundings.
A further factor which must be borne in mind is the fact that the atmosphere at the location may not be conducive to respiration at all. For example, at a fire, or in a mine shaft, the air will usually be heavily contaminated and scarcely fit to breath. It is therefore highly desirable that such contamination shall be completely excluded from the respiration equipment.
As stated, equipment has been available in the past of a relatively complex nature which would provide the positive pressure resuscitation function, applying 100 per cent oxygen under positive pressure to the casualty. However, it was difficult and cumbersome to convert such equipment to the inhalation function to permit free breathing with air enriched with oxygen after resuscitation had been successfully carried out. In addition, the control of such positive pressure apparatus required careful training and practice for satisfactory results which were not injurious to the casualty, for example, as a result of the application of an overpressure of oxygen to the lungs.
It is therefore desirable to provide a resuscitator apparatus which is simple to operate, and requires little or no training, and is designed to prevent accidental injury to the casualty, and which may readily be converted to an inhalator function by the operator without distracting his attention from the casualty.